Photobug,

Duplicates are a pain, no doubt. There are, I believe, some third-party solutions out there that will hunt through your Aperture Library, but I don’t have any experience with them. Ask the Great Google for something, or perhaps someone else here will have experience with one.

If the duplicates are the same name, looking at your library in List view might make it easier to find them. However look for similarities in the dupes, for example a keyword that’s on all (or most) duplicates, like “iPhoto Original”. Searching by those differences can help locate the dupes more quickly.

It’s not an easy task because unless a file is a byte-for-byte duplicate, there’s no guarantee that it is a duplicate, and that can make it very hard to be comfortable deleting files automatically.